# Introducation This library fully uses the advantages of decorators, make it smooth to write validation rules. This projects aims to be foundation component for the rest of [@t2ee](https://github.com/t2ee) projects. It provides dependency injection and auto configuration functionalities. # Installation `npm i reflect-metadata @t2ee/core @t2ee/validation -S` # Usage ## Example usage with [@t2ee/vader](https://github.com/t2ee/vader) ```typescript class Message { @NotNull @Min(4) message: string; } @Path('/') @Component class Controller { @POST @Path('/say') say(@Valid @Body message: Message) { // message should be at least 4 characters long } } ``` ## Example Custom Rule ```typescript const IsEmail = CustomRule('IsEmail', 'should be valid email'); @ValidationRule('IsEmail') class IsEmailRule implements Rule { validate(value: any, parameter: any, meta, AutoWireMeta, args: any[]): boolean { return /[\d\w]*\@[\d\w]*\.[\w]*/.test(value); } } ``` __OR__ ```typescript const IsEmail = Pattern(/[\d\w]*\@[\d\w]*\.[\w]*/); ``` # API ## @Valid `@Valid` is an essential decorator, it validates all the rules associated with a type. Without `@Valid`, validations will not be triggered. ## @CustomRule `CustomRule(name: string, error: string, parameter?: any) `, returns a `PropertyDecorator`. This binds necessary metadata to the class ## @ValidationRule and Rule `@ValidationRule(name: string)` inject your implementation of a rule to the `ValidationProvider`, where your rules are resolved, parsed and validated. `Rule` is a `interface` guides you how should it be implmeented for a `ValidationRule`. ## Rules ### @Length, @Max and @Min dataType | description ---------|------------- null or undefined | not checked String | checks the length of the string Number | checks Number.toString() length Array | checks array length Object | checks keys' length ### @NotNull Any value shuold pass validation if the value is not `null` nor `undefined`. ### @Pattern It only validates the regex when value is string and not `null` nor `undefined`.